Sensitizing dyes derived from 2-methyl-6-(2-carbamylethoxy)-benzothiazoles



United States Patent This invention relates to sensitizing dyes derived from 2'-methyl-6-(,B-carbamylethoxy)-benzothiazoles and to the silver halide emulsions sensitized with such dyes.

Benzothiazole'radicals which are substituted in the 6- position by a hydroxy, methoxy or carboxyethoxy, group have already been recommendedas intermediates in the preparation of certaincyanine dyes. However, the meth- 'ods described so far do notprovide benzothiazole nuclei in which a carboxamido group is attached to the 6-posi- 'tion of the benzothiazole by means of an ether linkage.

We have now found that extremely valuable sensitizing dyes can be prepared from benzothiazoles which contain a methyl group in the 2-position, a hydrogen atom or methyl group in the 5-position and a 'carbamylethoxy group in the 6-position. These bases, which are readily quaternized by conventional methods, can be reacted with cyclarnmonium quaternary salts containing a reactive group on them-carbon to produce, inter alia, monoand polymethine cyanine dyes which are valuable sensitizers for silver halide emulsions.

Among the objects of our invention are said sensitizing dyes and silver halide emulsions sensitized with said dyes. The bases which are used in the preparation of our dyes are 2-methyl-6-(,S-carbamylethoxy-benzothiazoles having the following generalstructure:

C-CHs and NO-'CHiCHiO- hydrolyzing agent. The reaction is illustrated by the following formulae';

wherein'R has the values given above.

The above obtained G-(fl-carbamylthoxy)-substituted benzothiazolebase may be readily'quaternized by-conventional methods to'pro'duce the desired cyclammonium quaternary salts "for the cyanine dye synthesis. 'For instance, the methiodide and the ethiodide are obtained by heating the base with methyl iodide or ethyl iodide, respectively, under pressure in a sealed container for'several hours at 962- ,C. The quaternary salts obtained are characterized by the following general formula:

E I /S I H N- -CH CH -0 Z 2 I R- wherein:R has the value given above; R is alkyl such as methyl, ethyl, propyl, fl-hydroxyethyl, 'y-hydroxypropyl, allyl and the like; carboxyalkyl, such as carboxymethyl, carboxyethyl and the like; aralkyl, e.g., benzyl, phenethyl and the'li'ke; and X is an anion such as chloride, bromide, iodide, methylsulfate, ethyl-sulfate, perchlorate, ptoluenesulfonate and the like.

The above quaternary ammonium salts may be con- 'verted into the sensitizing dyes which are characterized by the following general-formulae:

. wherein R and R have the values given above; m, n and p represent a 'positiveint'eger of from 1 to 2; R and R are either hydrogen or a lower alkyl group, e.g., methyl, ethyl, propyl and the like; R being only hydrogen when n and p equal 1; R represents an alkyl group such as methyl, ethyl, propyl, butyl, amyl; a hydroxyalkyl group such as hydroxymethyl, hydroxyethyl, hydroxypropyl and the like; carboxyalkyl such as carboxymethyl, carbonyethyl, carb'oxypropyl and the like; aralkyl, e.g., benzyl, phenethyl, "and the like; Y represents an anionic radical, e.g., Cl, .Br, 1,010 SO CH S0 C H SO C H.,CH and the likeyand Z represents the heteroatoms necessary to complete asor 6-membered nitrogenous heterocyclic system of the type usedin cyanine dyes, such as pyridine, lepidine, quinoline, indoline, oxazole,thiazoline,-thiazole,

- 3 selenazole, selenazoline, oxazoline, benzothiazole, benzoselenazole, benzoxasole, naphthothiazole and the like.

These sensitizing dyes are prepared by heating the above 6-(e-carbamylethoxy)-benzothiazolium salts in the presence of an acid binding agent such as pyridine, trimethylamine, triethlamine and the like with a cyclammonium quaternary salt having a reactive grouping on the carbon atom in the 2-position of the heterocyclic ring, for instance, a halogen atom, e.g., chlorine, bromide, or the like, and an alkylmercapto group, e.g., methylmercapto, ethylmercapto and the like; an alkylmercaptovinyl group, e.g., B-methylmercaptovinyl, fi-ethylmercaptovinyl and the like; a fl-alkylmercapto-B-alkylvinyl group, e.g., B- methylmercapto-fl-methylvinyl, fi-ethylmercapto-fi-ethylvinyl and the like; fi-acetanilidovinyl, 4-acetanilido, 3-butadienyl, and 6-acetanilido-1,3,5-hexatrienyl.

As examples of suitable cyclammonium quaternary cyanine dye salt intermediates having a reactive group in the 2-position to the nitrogen atom thereof so as to form a monomethine dye, the'following may be mentioned: 2-methylmercapto-6-methylquinoline ethiodide 1 2-methylmercapto-6-methoxyquinoline ethiodide 2-methylmercaptopyridine ethiodide 2-methylmercaptothiazoline ethiodide 2-phenylmercaptothiazoline ethiodide and the like.

' In preparing trimethine cyanine dye salts, the following cyclammonium quaternary cyanine dye salt intermediates having a reactive group in the fl-position of the side chain attached to the carbon atom in the 2-position of the heterocyclic nucleus may be employed: 2-(,B-acetanilidovinyl)-thiazoline ethiodide Z-(B-acetanilidovinyl)-benzothiazole ethiodide Z-(fi-acetanilidovinyl)-benzoxazole ethiodide 2- (B-ethyl-B-ethylmercaptovinyl) -5-meth0xybenzoselenazole ethiodide 2- B-methylmerc apto-B-methylvinyl) -benzothiazo1e ethiodide. 2-(,B-methylmercapto-}3-propylvinyl)-benzothiazole ethiodide In preparing pentamethine and heptamethine cyanine dyes, the following cyclammonium quaternary salts having a reactive group in the deltaand omega-positions of the side chain attached to the carbon atom in the 2-position of the heterocyclic nucleus may be employed:

2-(4-acetanilido-1,3-butadienyl)-pyridine ethiodide 2-(4-acetanilido-1,3-butadienyl)-benzoxazole ethiodide 2-(4-anilino-3-methyl-1,3-butadienyl)-pyridine ethiodide 2-(4-anilino-3-methyl-l,3-butadienyl)-fl-naphthoxazole ethiodide 2- (4-anilino-3-ethyl-l ,3-butadienyl) -t-113Phth0thlfl2016 ethiodide 2-(6-anilino-1,3-5-hexatrienyl) -thiazoline ethiodide 2-( 6-anilino-1,3,5-hexatrienyl -a-naphthothiazole ethiodide 2-( 6-anilinol ,3, 5 -hexatrienyl) -,8-naphthothiazole ethiodide 2-(6-anilino-1,3,5-hexatrienyl)-a-naphthoselenazole ethiodide 2- 6-anilino-1, 3,5 -hexatrienyl) -,3-naphthoselenazole ethiodide 2-(6-anilino-4-methyl-1, 3 S-hexatrienyl) -thiazoline ethiodide 2-( 6-anilino-4-methyl-1,3,5 -hexatrieny1) -benzothiazole ethiodide 2 6-anilino-4-butyl-1,3,5-hexatrienyl) -benzothiazole ethiodide We have found that our new dyes are especially useful for extending the spectral sensitivity of the customarily employed silver chloride, silver chlorobromide, silver bromide, silver bromoiodide and silver chlorobromoiodide developing out emulsions. The dyes are equally effective in gelatinous emulsions and in those emulsions in which a synthetic colloidal carrier such as modified polyvinyl alcohol is employed.

To prepare emulsions sensitized with one or more of our new dyes, it is only necessary to distribute homogenously the dye or dyes in the photographic emulsions. The methods of incorporating dyes in emulsions are simple and are well known to those skilled in the art. In practice, it is convenient to add the dyes to the emulsions in the form of a solution in an appropriate solvent. Methanol has proved satisfactory for our new dyes; dimethylformamide or a mixture of acetone and freshly distilled pyridine may also be employed as a solvent. The dyes are advantageously incorporated in the finished, washed emulsions and should be uniformly distributed throughout the emulsions.

The concentrations of dyes in the emulsions can vary widely; 'e.g., from 5 to milligrams per liter of flowable emulsion. The concentration of the dyes will vary somewhat according to the type of emulsion and according to the efiect desired. l

With most of our dyes, from 15 to 30 milligrams of silver halide) sufiice toprodu-ce the maximum sensitizing 'eifect. With the finer grain emulsions, somewhat larger concentrations of dye may beneeded to produce the maximum sensitizing effect.

The new dyes of our invention have been found to be particularly useful since they operate to increase the sensitivity of photographiuemulsions containing color formers fast to diffusion to a higher extent than comparable sensitizing dyes without the 6-cyanoethoxy-substituted benzothiazole nucleus. The sensitizing bands of the new dyes of our invention are unusaully sharp so that they render themselves advantageously for use in color emulsions.

The invention is further illustrated by the following examples although it is to be understood that the invention is not restricted thereto.

EXAMPLE I 2-Methyl-6-(fi-Cyanoethoxy)-Benzothiazole Eight grams (0.05 mole) of Z-methyl-G-hydroxybenzothiazole and 13.3 grams (0.25 mole) of freshly distilled acrylonitrile and 1 milliliter of benzyltrimethylammonium hydroxide (Triton B) were heated to reflux on a steam bath for 20 hours. T o the hot solution was then added milliliters of benzene and 2 grams of (bone) charcoal. The black slurry was heated to reflux temperature for 10 minutes and then filtered through a Buchner funnel. The charcoal on the filter was extracted with hot benzene, and the combined filtrates placed into a separatory funnel. The basic catalyst was removed by Washing. The benzene solution was washed with distilled water until the wash water was neutral to Alkacid paper. The benzene layer was then washed twice with 60 milliliters of a 2.5 percent aqueous sodium hydroxide solution in order to remove any unreacted 6-hydroxy-2-methylbenzothiazole. The benzene solution was subsequently washed again with water until the wash water was neutral and then dried with anhydrous sodium sulfate overnight. Removal of the benzene and any acrylonitrile by distillation under aspirator vacuum yielded 7.60 grams of crude prodnet. This material was crystallized from benzene. Yield: 6.6 grams; melting point 122-123". A second recrystallization from benzene did not raise the melting point.

NC-CHr-OHr-O- ANALYSIS FOR CnHmONzS enemas EXAMPLE n 2-Methyl-6-(B-Carbamylethoxy)-Benz0thiaz0le s mN- o' orncm-o- Ten milliliters of concentrated sulfuric acid and 2.18 grams (V mole) of Z-methyl-(B-cyanoethoxy)-benzothiazole were heated together until the temperature reached 80 C. The clear solution was allowed to stand for five minutes during which time it cooled down to 70 C. The solution was then poured into 80 milliliters of ice water and stirred. It was filtered to remove any C-CH:

mechanical impurities and then neutralized by add ng, dropwise, a 50 percent aqueous sodium hydroxide solution. Afterthe neutral point (pH 7.0) wa-s'reached,-2

milliliters of the'SO percent alkali hydroxide solution were added in excess. The alkali-insoluble 2-methyl-6- (fi-carbamylethoxy)-benzothiazole was filtered off and washed with distilled Water until the filtrate was neutral. Traces of 2-methyl-6-(fi-ca-rboxyethoxy)-benzothiazole formed by complete hydrolysis of the nitrile remained in the alkaline solution. After drying, 2.31 grams of 2- rnethyl-fi-(B-carbamylethoxy)-benzothiazole having a melting point of 179 to 181 C. was obtained.

' ANALYSIS FOR CuHrzOzNzS C H N Calculated 55. 90 5. 12 11. 86 Found 55. 86 5. 03 11.70

EXAMPLE III 2,5-Dimetlzyl-6-(fi-Carbamylethoxy)-Benz0thiaz0le s HiN("J--CHzCH2O.

CCH3 Example II is repeated except that the 2.18 grams of 6-(B-cyanoethoxy)-2-methylbenzothiazole are replaced by 2.32 grams of o-(fi-cyanoethoxy)-2,54limethylbenzothiazole.

EXAMPLE IV 6-(B-Carbamylethoxy)-2-Methylbenzothiazole Ethioiae EXAMPLE V 3- (fl-Carboxyethyl) -6-(/3-Carbamyleth0xy) -2,'5-D imethylbenzozhiazolium Iodide S ll HzN-C-CHz-CHz-O- C- -CH: OHa- /N\ (3112 I r Q0011 This product is ohtainedby hea ing LZgrams-of 2,5- .dimi hyl 6 (flwarbamylethoxy) benzothiazole and 10 grams of p-iodopropionic acid in a sealed bomb for 24 hours at 102 C. The resultant product is separated from the mother liquor by filtration and purified by trituration with ether, ethanol, acetone and again with ether.

EXAMPLE vr 3-Ethyl-6-(fl-Carbamylethoxy)-2-Methylbenzothiazolium p-Toluene Sulfonate C-CH: p I N/ Two grams each of, 6-(fiecarbamylethoxy)-2-methylbenzothiazole and ethyl p-toluenesulfonate; (20 percent excess) were melted'together and heated in a metal bath of about to C.for '3 hours.

After cooling to room temperature, the reaction mixture was dissolved in methanol, treated wtih charcoal and filtered. The methanol solution was-then evaporated to dryness and 3.6 grams of solid product was obtained.

PREPARATION OF DYES-EXAMPLE VII 1 ',3.-Diethyl-6-Methoxy-16'-(B Carbamyleth0xy) Thiapseudocyanine Iodide I? S OCH1 HaN-C-GHaClI-[rO C-CH t I CzH5 02115 I- One hundred fifty-six milligrams (0.4 millimole) of 6 (fl-carba-mylethoxy)-2-methylbenzothiazole ethiodide and milligrams (0.4 millimole) of Z-ethylmercapto- I 6-methoxyquinoline ethiodide were dispersed in 7 milliliters of methanol. 'Ten drops of triethylamine were added, and the mixture heated-on a steam bath'to dryness. One milliliter of anhydrous pyridine and 1 5 milliliters of methanol were added'in that order, :and the'mixture heated for 15 minutes on the steam bath. The slurry was centrifuged, and the mother liquor discarded. The dye was purified by successive extractions with methanolben zene (1:14) isopropanol and ether. After'drying,

" 150 milligrams of dye-were obtained having amelting point of 179 to 131" C. The methanol solution had-an absorption maximum at 501 millimicrons. This-compound sensitized a photog aphictgelatine silver bromideiodide emulsion to aboutjOO millimifcrons with a maximumsensitivity at about 480 millimicrons.

EXAMPLE VIII This dye was preparedfrom 156;. milligrams of 6 (3- carbamylethoxy) 2-methylbenzothiazole thiodide and3144 milligrams of 2-ethylmercapto-ormethylquiuoline ethic;

. dide following the procedure described in Example The yield wasalitfl-millig amsg.thezdye meltedat. -10

187 C. A methanol solution of the dye had an absorp- EXAMPLE XI tion maximum at 487 millimicrons. The dye sensitized S-Ethyl- '-(B-Carboxyethyl)-5'-Methyl-6'-(fl-Carbamyla gelatine silver bromide-iodide emulsion to about 500 ezhoxy)-Thiacarbocyanine Iodide door: 1-

millimicrons with a sensitivity maximum at 480 milli- Twenty-five drops of triethylamine were added to a microns. solution of 196 milligrams of 3-(fi-carboxyethyD-6-(flp EXAMPLE IX carbamylethoxy)-2,5-dimethylbenzothiazolium iodide and 4',5-Benzo-6-(,B-Carbamylethoxy)-3,9-Diethyl-3'- 216 milligrams of Z-(fi-acetanilidovinyl)-3-ethylbenz0- Methylthiaca rbocyanine Iodide thiazolium iodide in 20milli1iters of ethanol. The prod- 3: i i V a 7 S H:N CHgCH:-O i 2 5 COH=( -CH=O 3H5 Ha One hundred fifty-seven milligrams (0.4 millimole) of net which separated on cooling was centrifuged and then 6 (fi-carbamylethoxy)-2-methylbenzothiazole ethiodide Washed with ethanol, acetone and ether. and 171 milligrams (0.4 millimole) of 4,5-benzo-2-(B ethyl B-methylmercaptovinyl)-benzothiazole ethiodide EXAMPLE XII were dispersed in 7 milliliters of methanol to which ten 6'-(B-Carbamyleth0xy)-3,3'-Diethyl-5,6-Dimethyl Oxadrops of triethylamine were then added. The mixture thiacarbocyanine Iodide E HgN- -CH:OH2O CH;

O /C--CH=CHC=O\ CH; N III/ 52H! 03H 1- was heated to reflux for minutes on a steam bath. One hundred seventy-five milligrams of 3-ethyl-6-(B- The slurry was placed into a centrifuge glass and the carbamylethoxy)-2-methylbenzothiazolium p-toluenesulsolid separated from the mother liquor by centrifuging. fonate and 185 milligrams of Z-(B-acetanilidovinyl)-3- The solid was purified by successive trituration with a ethyl-5,6-dimethyloxazolium iodide were dissolved in 20 mixture of methanol, benzene (1:14), isopropanol and milliliters of methanol. Twenty drops of triethylamine ether. After drying, 140 mg. of dye was obtained which were added. The mixture was heated to boiling and then melted at 148-l50 C. The methanol solution of this evaporated to dryness on a steam bath. The mixture was dye had anabsorption maximum at 571 millimicrons. successively triturated with ether, isopropanol, acetone The'compoundssensitized a photographic gelatine silver and again with ether. The dye melted at 280-282 C.

bromide iodide emulsion to about 665. millirnicrons with The methanol solution showed an absorption maximum at the maximum sensitivity at about 645 millimicrons. 530 millimicrons. This dye sensitized a gelatine silver bromide iodide emulsion to about 590 millimicrons with EXAMPLE X a maximum sensitivity at about 580 nnlllmicrons. '-(fly y)- 'fl-IflflMl-S-Methoxy- Various modifications of this invention will occur to selenathracarbocyanme Iodzde persons skilled in the art. Thus, our intermediates can f 8 Se mN-c-cmcm-of C--CH=OCH=D N N CaHr :Hs

This dye is prepared by reacting 156 milligrams of be used not only for the preparation of monoand poly- 6 (fi-carbamylcthoxy)-2-methylbenzothiazole ethiodide m'ethine dyes of the types illustrated by the examples, (0.04 millimole) with 187 milligrams (0.4 millimole) of but lend themselves also to the preparation of mero- 2 (fl ethyl-fl-methylmercaptovinyl)-5-methoxybenzocyanine and styryl dyes. We, therefore, do not intend selenazole ethiodide under the conditions described in to be limited in the patent granted except as necessitated Example IX. After drying, 160 mg. of dye were obtained by the appended claims. which melted at 145-147 C. The methanol solution This application is a continuation-in-part of our cohad an absorption maximum at 570 millimicrons. The pending application, Serial No. 732,835, filed May 5, dye sensitized a photographic gelatine silver bromide 1958, now United States Patent 2,984,667.

iodide emulsion to about 635 millimicrons with a maxi- We claim:

mum-sensitivityof about 620 millimicrons. I 1. Sensitizing dyes selected from the group consisting wherein R is a member selected from the class consisting A snsmzmg dye having fouowmg formula' of hydrogen and methyl; R and :R are members selected s S from the group consisting of methyl, ethyl, propyl, butyl, -B 02H: amyl, hydroxymethyl, fi-hydroxyethyl, a-hydroxypropyl, C CH= carboxymethyl, carboxyethyl, allyl, benzyl and phenethyl;

R and R represent members selected from the group N N consisting of hydrogen, methyl, ethyl and propyl; R, A H 1 being only hydrogen when n and p equal 1; m, n and p I 5 represent positive integers ranging from 1 to 2; Y repre- 4. A sensitizing dye having the following formula:

E OYH HiN- -cH,0H,-o 2

/C-CH=Jl-OH=C\ -0 CH3 r l CnHs I 02H: 1 'sents an anionic radical of the type used in cyanine dyes, 5. A sensitizing dye having the formula formula: and Z represents the atoms necessary to complete a nitrog- 0 o 'enous heterocyclic nucleus selected from the class cong HzN- -OH :OH2O

i n r'din nucleus .a le idine nucleus a nines su g of a py 1 e P q Q-OH=OHCH=O line nucleus, an indoline nucleus, an oxazole nucleus, at 40 thiazoline nucleus, a thiazole nucleus, a selenazole nucleus, a selenazoline nucleus, an oxazoline nucleus, 9. benzothiazole nucleus, a benzoselenazole nucleus, a benz- I oxazole nucleus, and a naphthothiazole nucleus.

2. T sensitizing dye having the following formula: 0 OH I' I! 0cm HNwwmonro' References Cited in the file of this patent 3 UNITED STATES PATENTS E 2,984,667 Horwitz et al. May 16, 1961 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,080,363 March 5, 1963 Lester Horwitz et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 33, for "({3carbamylethoxy" read (gcarbamylethoxy) column 3, line 6, for "triethlamine" read triethylamine column 5, line 49, for "Ethioide", in italics, read Ethiodide in italics; line 58, for "mlililiters" read milliliters column 10, line 36, for formula", first occurrence read following Signed and sealed this 7th day of January 1964.

EAL)

Est! EDWIN L. REYNOLDS JEST W. SWIDER esting Officer A 1 1 n Commissioner of Patents 

1. SENSITIZING DYES SELECTED FROM THE GROUP CONSISTING OF THOSE HAVING THE FOLLOWING FORMULAE:
 3. A SENSITIZING DYE HAVING THE FOLLOWING FORMULA: 